ChemCatChem最新文献

Single-atom catalysts (SACs) demonstrate high selectivity, maximal atom utilization, and unique active site configurations, establishing them as a rapidly expanding research field. Understanding the intrinsic relationship between structure and catalytic performance is crucial for the effective use of SACs in catalysis. However, providing a clear explanation of the coordination environment and intrinsic structural regulation of SACs remains a significant challenge for next-generation renewable energy materials, especially in advanced oxidation and reduction processes critical for sustainable energy applications. This comprehensive review offers an in-depth overview of the current progress and design of SACs, with a specific focus on precise synthesis, structural control, and the relationship between structure and performance. Furthermore, we elucidate the reaction mechanisms of various catalytic systems and the selective methods used to precisely synthesize and enhance catalytic reactions in the sustainable energy sector. Finally, this review explores the complex challenges in investigating and developing SACs and offers a perspective on solutions in advanced oxidation and reduction technologies for future research to overcome these challenges and achieve practical applications.

Photothermal dry reforming of methane (PT-DRM) is an appealing pathway to convert carbon dioxide and methane into synthesis gas, a mixture of carbon monoxide and hydrogen, via photothermal heating induced by concentrated sunlight. However, coke formation and sintering of active metal nanoparticles are key issues for catalyst stability. In the present study, we demonstrated Co–Ni alloy nanoparticles encapsulated with a porous SiO₂ shell exhibited improved catalytic activity and stability for PT-DRM using visible/near-IR light irradiation without any other external heating. The addition of a tiny amount of Co (1–5 mol% relative to total metal) and SiO₂ encapsulation enhanced the stability by simultaneously suppressing coke formation and sintering of the metal nanoparticles. Furthermore, we revealed that the position of the light irradiation spot has a crucial role in the conversions of methane and carbon dioxide and product selectivity, presumably due to the large temperature gradient under the light irradiation. These findings would contribute to designing effective PT-DRM catalysts with improved activity and enhanced resistance for both coke formation and sintering and emphasize the significant contribution of the temperature gradients to the performance of PT-DRM.

The reaction of N,N-bis(2-(diisopropylphosphaneyl)ethyl)prop-2-yn-1-amine 1 with [Ru(CO)ClH(PPh₃)₃] leads to the formation of a new class of cyclometallated PNPC pincer complexes. Several examples of this class of compounds are synthesized and characterized. They, specifically complexes 2 and 3, show good to excellent activity and selectivity in additive-free formic acid dehydrogenation, and transfer (de)hydrogenation reactions of different functional groups (ketone, alkyne, and alcohol). Theoretical and experimental studies reveal two competing pathways for the dehydrogenation of formic acid. The Ru-H pathway proceeds via the coordination site trans to the propylene arm of the ligand, whereas in the Ru-C pathway, a de-coordination of the propylene arm is observed.

The influence of the support on the performance of Mo nitrides has been investigated in ammonia synthesis and decomposition. A series of Mo–N catalysts supported on different materials, namely SiO₂ (commercial, SBA-15), Al₂O₃, and CeO₂, were prepared. The results indicated that, despite the high dispersion of Mo species in all catalysts, large disparities in the activity for ammonia synthesis exist. Initial rates of ∼1208, ∼481, and ∼372 µmol g_{active phase}⁻¹ h⁻¹ are obtained over 10-Mo–N/SBA-15, 10-Mo–N/SiO₂, and 10-Mo–N/Al₂O₃ respectively. However, no catalytic activity was registered when Mo species were supported on CeO₂. Furthermore, 10-Mo–N/Al₂O₃ deactivated after few hours of reaction. The surface composition was studied by means of XPS to probe the origin of the catalytic activity differences, and the results indicated that a range of various oxidation states of Mo was detected depending on the support. The difference in catalytic behavior could not be solely explained by the differences in Mo–N species concentrations. In situ EPR analysis exhibited that the mechanism of MoO₃ nitridation could differ depending on the support, leading to the formation of different Mo–N species. The effect of support was, however, not as severe in ammonia decomposition as it was the case of ammonia synthesis.

Photocatalysis is an efficient technology for the degradation of pollutants. However, it still needs to be improved. In this study, magnetic Z-scheme FeP/CdS composites heterojunction photocatalysts were prepared by a facile hydrothermal method, and the structure, morphology, optical, and photocatalytic properties of the prepared composites were investigated in detail. The efficiency of tetracycline hydrochloride (TCH) removal by FeP/CdS composites was investigated under different reaction conditions (including different FeP and CdS ratios, catalyst dosage, hydrogen peroxide consumption, temperature, and initial pH). FeP/CdS composites exhibited better catalytic performance compared with pure components. The F₁Cd₁ composite (mass ratio of FeP to CdS is 1:1) achieved 92.7% removal efficiency of TCH; moreover, the F₁Cd₁ composite still exhibits a high stability after five consecutive cycles. The capture experiments on the active material showed that the removal of TCH by the F₁Cd₁ composite was mainly dominated by •OH; however, •O₂⁻, e⁻, and h⁺ played a minor role, and the degradation mechanism was revealed by combining various characterization techniques. The introduction of cadmium sulfide formed an effective photogenerated carrier transport channel at the interface with the iron phosphide surface, which could accelerate the transfer and separation of photo-excited e⁻/h⁺ pairs, thus improving the degradation performance of TCH.

Enzymatic recycling of polyethylene terephthalate (PET) has attracted significant attention in recent years. While the fusion of anchor peptides to PET hydrolases is believed to enhance PET hydrolytic activity, a quantitative analysis is yet lacking. Here, we construct four fusion enzymes by fusing anchor peptides (including hydrophobic LCI, LCIM1 and TA2, and hydrophilic EK4) to the C terminus of HotPETase, one of the most active PET hydrolases for high-crystallinity PET (HC-PET). Single-molecule force spectroscopy (SMFS) demonstrates that hydrophobic anchor peptides promote adhesive interactions between the fusion enzymes and the PET surface. This is also validated by the adsorption kinetics and isotherms, and the saturated adsorption capacity remains unaltered compared to HotPETase. At low substrate loadings, the apparent hydrolytic activity of these fusion enzymes is positively related to the hydrophobicity of the anchor peptides. Among them, HotPETase-LCI stands out as the most effective enzyme for HC-PET degradation, demonstrating a 1.5-fold increase in hydrolytic activity. At high substrate loadings, the advantages of fusion with anchor peptides diminish. We conclude that fusion enzymes only facilitate the hydrolytic rates of reactions for HC-PET but have little effect on the final conversion extent.

Elevated levels of reactive oxygen species (ROS) are a hallmark of varieties of diseases such as cancer, inflammation, and neurodegenerative disorders. Inspired by the discrepancy of ROS concentrations between pathological tissues and the normal counterparts, an increasing number of ROS-responsive theragnostic prodrugs are developed in past years, with particularly high proportions of organoboron-based prodrugs that can respond to H₂O₂. Unfortunately, increasing studies have demonstrated that the intrinsic ROS (H₂O₂) levels in most pathological tissue are only slightly higher than normal tissues and are not adequate to activate organoboron prodrugs; in contrast, several organoboron compounds have been clinically approved in which boronic acid acts as electrophilic warhead. To this end, developing more robust and universal approaches for boronic acid-prodrug activation becomes highly attractive. In this context, we discuss the recently reported activation strategies for boron-caged prodrugs with a particular focus on their design principles and activation mechanisms. The perspectives on the future directions for this important research area are discussed as well.

Three pyrene-4,5,9,10-tetraone-based porous aromatic frameworks (PT-PAFs) are synthesized and their photocatalytic properties for H₂O₂ production are studied. It is found that the combination of pyrene-4,5,9,10-tetraone with anthraquinone affords an efficient PT-PAF photocatalyst (PAF-371) for H₂O₂ production, which achieves production rates of 3791 µmol g⁻¹ h⁻¹ (with sacrificial reagent) and 923 µmol g⁻¹ h⁻¹ (without sacrificial reagent) from water and oxygen under visible light irradiation. This work demonstrates that pyrene-4,5,9,10-tetraone molecule could be introduced into PAF materials to construct efficient organic semiconductor photocatalysts for H₂O₂ production.

In the field of olefin polymerization catalysis, metallocenes are heterogenized with methylaluminoxane onto silica supports to yield active catalysts. During olefin polymerization, these silica supports act as a framework to control the fragmentation stage, thereby influencing the final polymer product and preventing reactor fouling and fines formation. This study investigates the influence of different silica supports induced on the final polymer product. To study a broad range of silica supports from an industrial silica database, we utilize a hierarchical clustering method to cluster the supports based on their physical properties. From the clustering method, five supports representing the clusters and an industrial benchmark were analyzed at different polymerization stages using focused ion beam–scanning electron microscopy (FIB–SEM) and microcomputed tomography (microCT). This combined FIB-SEM/microCT methodology revealed differences in both fragmentation behavior and polymer morphologies based on structural features, including macropores, mesopores, spray-dried shells, spray-dried spheres, and denser shells. The heterogeneity and ideal fragmentation behavior was further assessed by calculating the replication factor of each support, indicating that silica materials containing macropores and spray-dried shells have an almost ideal replication phenomenon. This multiscale analysis revealed new understanding of catalyst fragmentation for different supports. This understanding could in the future be further developed by the addition of more supports or additional analysis of the supports to the industrial database.

Controlling the metal geometric and electronic structure is of significance in developing efficient catalysts for heterogeneous hydroformylation. This study examines the structural sizes of Rh and Rh⁺-Rh⁰ distribution to construct a highly active catalyst for formaldehyde hydroformylation. The active sites for hydroformylation require several Rh_n atoms, while single-atom Rh can solely catalyze hydrogenation. The highest activity was achieved on Rh nanoclusters (0.95 nm), giving a TOF of 191 h⁻¹ and selectivity of 82% for glycolaldehyde formation. The tunability of the electronic properties of Rh nanoclusters and the synergistic interaction between Rh⁺ and Rh⁰ are essential for enhanced activity. Pseudo-in situ FT-IR analysis elucidated that formaldehyde adsorbed on Rh nanocluster prefers to produce glycolaldehyde via hydroformylation, while formaldehyde adsorbed on isolated Rh^δ+ sites tends to form methanol via hydrogenation. This study provides a new insight into the design of heterogeneous catalysts and guidance for understanding the reaction mechanism for aldehydes/olefins hydroformylation.